Solanum sisymbriifolium aka Sticky Nightshade

Solanum sisymbriifolium, or sticky nightshade, belongs to the nightshade family, Solanaceae. It comes from South America, including southern tropical regions. Its native climate has a dry season. It now grows wild beyond its native range. In southeastern North America, it grows on waste ground near ports. Other names include red buffalo bur and morelle de Balbis.

This bushy plant grows upright, with stems that can turn woody. It may live one year or persist as a short-lived perennial. Garden plants reach 3.3–4.9 feet [1–1.5 metres] tall. They spread about 1.6–3.3 feet [0.5–1 metre]. Botanical accounts also record plants just 1.3 feet [0.4 metres] tall. Plants reach their full size within one to two years. The leaves have deep lobes and a coat of sticky hairs. Red prickles cover both the leaves and stems. The plant sheds its leaves rather than keeping them year-round.

Clusters of large flowers appear through summer in temperate gardens. Their colour ranges from white to pale blue. In tropical climates, flowering and fruiting can continue throughout the year. Green, prickly cases enclose the young berries. Each case is an expanding calyx that opens as fruit ripens. The exposed berries turn bright red and have a rounded shape. They measure about half an inch across. Sources list the fruit as edible, though its flavour is bland. The evidence does not establish other parts as safe to eat. Reports describe leaf and root infusions in local medicine. These records do not establish their safety or effectiveness.

Give this plant full sun and shelter in the garden. It needs moist soil that drains well. Clay, loam and sand can all suit it. Neutral to slightly alkaline soil meets the RHS guidance. Its UK hardiness rating is H2: it tolerates chill, but not freezing. Gardeners in temperate regions grow it as a spring-sown annual. It can persist where frost is rare. Raise new plants from seed; routine pruning is not needed.

Its bold form suits beds, borders and informal gardens. The RHS also lists it for wildlife gardens. Growers have tested it against potato cyst nematode as a trap crop. Few pests trouble it, though honey fungus can occur. Heavy seed production can make it a garden nuisance. It also forms dense stands in pastures that grazing animals avoid. It has spread as a weed across several climate zones. South Africa classes it as a noxious weed. That weed risk matters alongside its garden and crop uses.